Thermodynamics of Electrolytes. III. Activity and Osmotic Coefficients for 2-2 Electrolytes

The peculiar behavior of 2-2 and higher valence type electrolytes is discussed in terms of various theories some of which assume, while others do not, an equilibrium between separated ions and ion pairs as distinct chemical species. It is recognized that in some eases a distinct species of inner-shell ion pairs is indicated by spectroscopic or ultrasonic data. Nevertheless, there are many advantages in representing, if possible, the properties of these electrolytes by appropriate virial coefficients and without chemical association equilibria. It is shown that this is possible and is conveniently accomplished by the addition of one term to the equations of Parts I and H of this series. The coefficients of these equations are given for nine solutes. It is also noted that these equations have been successfully applied to mixed electrolytes involving one component of the 2-2-type.